Under an intermediate-system to an intermediate-system (IS-IS) protocol, a link state protocol data unit (LSP) packet is mainly used to notify of topology and routing information. The IS-IS protocol typically calculates a topology based on a shortest path algorithm (e.g., Dijkstra) and performs route calculation for Internet Protocol version 4 (IPv4) or Internet Protocol version 6 (IPv6) according to the calculated topology to direct data packet forwarding. The IS-IS protocol has been used in existing IP networks to support various applications of IPv4 and IPv6. IPv4 address assignment, however, cannot satisfy the requirements of ever-expanding networks and mixed networks of IPv4 and IPv6 have been implemented in some areas. In addition, in various applications, the topology for IPv4 may not be consistent with the topology for IPv6. As such, routing calculation errors often arise in these types of applications because a link supporting IPv4 may be identified as a link supporting IPv6 or vice versa. In other instances, a link supporting IPv4 may be also be identified as a link that supports IPv6.